Receiver Operates in PPG-Only mode at Approximately 1-μA/Hz Sampling Rate

Power-Down Mode: Approximately 0 μA

PPG Transmitter:

Four LEDs in Common Anode Configuration

8-Bit LED Current Up to 200 mA

Mode to Fire Two LEDs in Parallel

Programmable LED On-Time

Simultaneous Support of Three LEDs for SpO2, or Multiwavelength HRM

Average Current of 30 μA Adequate for a Typical Heart-Rate Monitoring Scenario:

20-mA Setting, 60-μs Pulse Duration, 25-Hz Sampling Rate

Clocking Using an External or Internal Clock

FIFO With 128-Sample Depth for ECG and PPG

I2C, SPI™ Interfaces: Selectable by Pin

Operating Temperature Range: –20°C to +70°C

2.6-mm × 2.1-mm, 0.4-mm Pitch DSBGA Package

Supplies:

Rx: 1.8 V to 1.9 V (LDO Bypass), 2.0 V to 3.6 V (LDO Enabled)

Tx: 3 V to 5.25 V

IO: 1.7 V to Rx_SUP

2 Applications

Synchronized PPG, ECG for Blood Pressure Estimation

HRM for Wearables, Hearables

Heart-Rate Variability (HRV)

Pulse Oximetry (SpO2) Measurements

3 Description

The AFE4900 device is an analog front-end (AFE) for synchronized electrocardiogram (ECG), photoplethysmogram (PPG) signal acquisition. The device can also be used for optical bio-sensing applications, such as heart-rate monitoring (HRM) and saturation of peripheral capillary oxygen (SpO2). The PPG signal chain supports up to four switching light-emitting diodes (LEDs) and up to three photodiodes (PDs). The LEDs can be switched on using a fully integrated LED driver. The current from the photodiode is converted into voltage by the transimpedance amplifier (TIA) and digitized using an analog-to-digital converter (ADC). The ECG signal chain has an instrumentation amplifier (INA) with a programmable gain that interfaces to the same ADC. A right-leg drive (RLD) amplifier set can be used to the bias for the ECG input pins. AC and dc lead-off detect schemes are supported. The ADC codes from the PPG and ECG phases can be stored in a 128-sample first in, first out (FIFO) block and read out using either an I2C or a serial programming interface (SPI) interface.

For all available packages, see the package option addendum at the end of the datasheet.

SPACE

Simplified Block Diagram

4 Device and Documentation Support

4.1 Trademarks

All trademarks are the property of their respective owners.

4.2 Electrostatic Discharge Caution

This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage.

ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications.